The present invention relates to a torque-limiting control device, plus an aerodynamic brake in particular for the application in vertical axis wind turbines and a means for thermally deicing vertical axis wind turbine air foils.
In the course of the rapidly growing onward development of the usage of wind energy, it is a common desire to design wind energy plants and wind energy systems respectively, in a more efficient way. However, the control of wind energy plants under strong wind conditions is a noted problem, regardless if they are designed as vertical axis wind turbine 14 (VAWT) or horizontal axis wind turbine (HAWT). Known vertical axis wind turbines are e.g. Savonius wind turbines or Darrieus wind turbines (mostly giromill wind turbines). It has to be noted that rotors for vertical axis wind turbines are not to be understood in the sense of a propeller, but rather as wing-like driving airfoils and vertical airfoil runners respectively, or resistance runners, i.e. anemometers, which are purely driven by their drag. Vertical airfoil runners follow the active principle of the generation of ascending force like an aircraft wing—yet the ascending component does not act against the gravity (like at an aircraft), but, as it is known to a person skilled in the art, 90° horizontally to the gravity vector, thus transforming lift into torque in order to propel the turbine.
Mainly at high wind speeds the rotation speed of the rotor has to be limited to prevent damage or destruction of the wind energy systems caused by exceeding wind energy. Furthermore, there has to be a possibility to shut down wind energy systems for maintenance work and repair work, even if wind energy drives the wind energy systems at the same time. Thus, it is important that each wind energy system comprises a brake device. However, conventional brakes such as wheel disk brakes or drum brakes are not adequate since they are subjected to high wear. Furthermore, a permanent brake capacity has to be ensured. Friction-based brakes may heat up themselves until brake failure occurs. This problem may be solved in the prior art by the use of wear-free eddy current brakes. However, a problem results in that eddy current brakes may not permit individual control and they are ineffective at power failure or control failure. Systems according to prior art having adjustable rotor-blades may not be turned away from the wind any more at power failure or control failure so that the wind energy may still continue to drive the rotor to self-destruction. Thus, there is a need for wind energy plants having a self-governed automatic brake activation and automatic shut down respectively, in case of malfunction situations. In the prior art, an additional problem results if an emergency situation occurs, e.g. a lightning strike, and the electric control devices fail so that a shut down of the wind-turbine (HAWT and/or VAWT) becomes impossible.